Many forensically important calliphorids, sarcophagids and muscids (Diptera) oviposit or larviposit on corpses only during the early stages of decomposition, yet individuals may attend bodies throughout decay. A field study was conducted to investigate how patterns of carcass use and attendance by some fly species are affected by decomposition. Five fly traps were placed in the forest and baited with whole, fresh piglet carcasses. Piglets decomposed in traps throughout the experiment, and all were skeletonized within 6 days. Flies were trapped at both early and late decomposition stages, and the species and population structures of trap catches were compared. More flies attended carcasses early rather than late in decay. For all species, flies attending early were mainly gravid females, but few gravid females attended late in decay. No females ovi- or larviposited late in decay, whereas females of all fly species deposited offspring early in decay. The number of males trapped of each species correlated positively with the number of females with eggs at early development stages. Observations were made of fly predation by European wasps Vespula germanica Fabricius (Hymenoptera, Vespidae) and jumper ants Myrmecia pilosula Smith (Hymenoptera, Formicidae) throughout the experiment. There was a higher risk for smaller fly species of being killed following predator attack. Ants and wasps attacked smaller fly species, whereas only wasps attacked larger fly species.

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A succession of insect species associate with decaying bodies, and because of the relatively predictable arrival and departure times of many species, this process is routinely used to estimate minimum post-mortem interval. Corpse fauna are compared with baseline data on succession rates, which are usually taken from decomposing animal carcasses. Baseline data are traditionally collected over a single year only; however, annual differences in weather patterns and insect population parameters probably alter succession rates. Surprisingly, this potential source of error has not previously been examined. Therefore, a two-year succession experiment was performed to investigate annual variation in succession rates. Sets of five still-born piglet carcasses were placed in a forest each season of both years. Six insects that occur year-round were selected: adults of Aleochara brachialis Jekel, Anotylus spp., Creophilus erythrocephalus Fabricius (Staphylinidae: Coleoptera), Ptomaphila lacrymosa Schreibers (Silphidae: Coleoptera), Pseudonemadus spp. (Leiodidae: Coleoptera), and larvae of Calliphora spp. (Calliphoridae: Diptera). Arrival and departure weeks to and from carcasses were measured in each season of both years. Two-way ANOVAs revealed significant season and year interactions on the arrival weeks of Anotylus spp., C. erythrocephalus, and Pseudonemadus spp., and significant differences in seasonal and yearly arrival times for A. brachialis, and P. lacrymosa. For larvae of Calliphora spp., there was a significant seasonal effect on arrival times. A significant interaction between season and year affected the departure weeks of all taxa. These results show that error in the estimates of minimum post-mortem interval can result if baseline succession data are collected only over one year.

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